COVID-19 Vaccines: What the Scientific Experts Say

Image: Gerd Altmann (Pixabay)


1. The Royal Society[1]: The Race for a Vaccine[2] (28 January 2021).

2. ZOE Symptom Study[3]: COVID-19 Vaccines: What we know so far[4] (3 February 2021).

3. University of Southampton[5]: Beating COVID-19 - Vaccines, Trials and Prevention[6] (9 February 2021).

What are COVID-19 and SARS-CoV-2?

Viruses comprise either ribonucleic acid (RNA) or deoxyribonucleic acid (DNA). COVID-19 is caused by a coronavirus that is RNA based. Coronaviruses are typically respiratory viruses, replicating in the airways. Four coronaviruses circulate yearly, resulting in cold-like symptoms, whereas SARS, MERS and COVID-19 can cause serious illness[2]. SARS-CoV-2 uses its spike proteins (as a key) to enter our cells through ACE-2 receptors (a doorway). It then hijacks our cells’ machinery to replicate and spreads to other cells in our body. COVID-19 develops if there is a high enough viral load within the body.

COVID-19 is a biphasic disease - it has two main phases:

1. Viral replication: Initial illness for about a week, before the patient starts feeling better[2].

2. Inflammatory response: Severity depends upon how successfully the immune system halted viral replication - the lower the viral load, the milder the symptoms[2].

Graphic of SARS-CoV-2 viral particle. Image: Joseph Mucira (Pixabay)

Why vaccinate against COVID-19?

Vaccines produce stronger and longer-lasting immunity than naturally acquired immunity from previous infection[2, 6]. Incurring both types of immunity provides a cumulative effect, offering greater protection[6].The vaccines approved so far should prevent hospitalisations and death in most cases[6].

COVID-19 has caused long-lasting problems in some patients’ organs, especially the brain and lungs. The long-term health costs from COVID-19 outweigh any potential vaccine long-term risks[4].

The immune system

1) Innate immune defence:

This first-line (non-specific) defence is constantly alert for invaders. If a threat is identified, the innate immune system cells search for and kill infected host cells and protect others from infection[7]. In viruses, the lower the viral load, the milder the symptoms. But SARS-CoV-2 suppresses the innate response resulting in an increased viral load[2].

2) Adaptive immune defence:

This secondary response is very specific to the invader (e.g. SARS-CoV-2). The major players are:

· B cells: Antibodies attach to the virus and label it for destruction[7].

· T cells: Kill infected cells, activate other immune cells and support the antibody response[7].

These cells have a subgroup of memory cells tasked with remembering the specific virus and learning to combat it better next time the virus is encountered[7]. It is expected that COVID-19 vaccines should lengthen the immune response to about a year instead of a few months[2, 4, 6].

Types of vaccine

The main types of COVID-19 vaccines are:

1. Replication-incompetent vector (Astra-Zeneca, Janssen): An inactivated cold virus producing a spike protein. An immune response is mounted against the spike protein and cold virus[6]. (Used against SARS and MERS[4]).

2. RNA (Pfizer, Moderna): RNA (in this case mRNA or messenger RNA) produces a spike protein from the genetic material carried inside a “lipid particle”. The lipid particle aids the immune response. (Used previously in anti-cancer vaccine research)[6].

3. Recombinant spike protein base (Novavax, Medicago GSK): The spike protein is created in a lab and transported in an “adjuvant” (immune enhancer) to create a stronger immune response. (Fairly traditional method[6].

4. Inactivated virus (Valneva): The virus is grown in a lab, killed and inactivated. This method might be useful against spike protein mutations. (Traditional method)[6].


Vaccine efficacy (efficiency) percentages indicate the ability of the vaccine to protect against developing COVID-19. It is difficult to compare efficacy between COVID-19 vaccine studies, because researchers use different groups of people and measurements to assess their particular vaccine[4, 6].

Image: Belova59 (Pixabay)

Fast vaccine development

At first sight, ten months to develop, test and approve vaccines seems remarkably quick when compared to previous vaccine development. However, this timeframe seems reasonable when it is considered:

· There was huge worldwide government investment (billions of US dollars) - usually there are long delays waiting for funding to trickle through[2].

· The three trial phases ran in parallel - usually they take place one after the other[2].

The World Health Organization was integral in coordinating the development of new COVID-19 treatments and vaccines[10]. The UK’s “Medicines and Healthcare Products Regulatory Agency” (MHRA) is the global expert, previously ensuring vaccine safety for the whole of the European Union. Any uncertainty about vaccine approval is not about safety, it is about how well the vaccines will work and for how long[6].

How vaccines work

2. Second dose: Boosts the immune response, making it stronger and longer lasting. Memory cells recognise the SARS-CoV2 spike protein, produce improved antibodies and memorises them for next time they are needed[2].

12-weeks between vaccine doses

There was no medical reason for Pfizer choosing three weeks between doses - presumably, it was to enable faster turnaround for their vaccine release[6]. It was thought Pfizer vaccines would likely perform comparably to Astra-Zeneca, because they elicit a similar immune response[4].On the 18 February 2021, evidence from Israel’s Pfizer vaccinations reported the second dose could potentially be delayed, because the first dose provides adequate interim protection, but advised more long-term follow-up was needed[11].

Image: mohamed Hassan (Pixabay)


Vaccine suitability

Previous infection with SARS-CoV-2:

It is likely the first vaccine dose would improve the immune response in those recently infected with the virus (up to six months ago) compared to those who have not been exposed[4]. COVID “long-haulers” should be safe to take the vaccine, because ongoing symptoms are an inflammatory response, not the virus itself[4].

Autoimmune diseases and immune suppressants:

People with autoimmune diseases or prescribed immune suppressants are not usually included in vaccine trials, because they skew the study results, rather than concerns over their safety. Therefore, according to Professor Tim Spector, the vaccines should be safe for this group[4].

Astra-Zeneca and the over 65’s:

Astra-Zeneca was tested on a limited number of over 65’s, because many in this group were advised to shield at the time trials were commencing. Therefore, it seemed inappropriate to ask most of this group to attend research centres[4]. On 15 February 2021, the World Health Organization recommended Astra-Zeneca for adults of all ages based on the available study results[12].

Vaccine side effects

The UK’s Joint Committee on Vaccination and Immunisation (JCVI) assessed the Astra-Zeneca vaccine based on millions of doses - their results showed exceptionally good safety. Up to 1,000 reactions are considered normal, but for the Astra-Zeneca trials, there were only the usual immediate minor side effects (e.g. sore arm, fever) and no hospital admissions[6]. Any vaccine side effects of concern are expected to occur fairly immediately; therefore, people usually wait fifteen minutes after vaccination before leaving the vaccination centre[2].

Common side effects:

As with most vaccines, common minor side effects can occur soon after vaccination and may last a few days. The most common is a sore or slightly swollen arm near site of injection. A smaller proportion, experience systemic effects, including headache, fever and/or fatigue. Systemic effects are more likely after the second (booster) dose, because the immune system is already primed to recognise viral proteins[4]. These symptoms indicate the immune system is developing protection. People are more likely to experience side effects if they are anxious about them, even with the placebo saline injection (placebo effect). Symptoms are eased with paracetamol[4].

Side effects due to previous COVID-19 exposure:

Individuals who had previously experienced Covid-19 were twice as likely to experience systemic side effects after the first vaccine. This suggests in these circumstances, the primer (first dose) acts like a booster (second dose), as the immune system was already primed by prior natural exposure to SARS-CoV-2. Consequently, these individuals could have more protection, closer to that experienced after the second dose. It is still safe to have the second booster dose[4].

Image: Wilfried Pohnke (Pixabay)

Mixing vaccines

New variants

If enough people are vaccinated, variant concerns will be less relevant, because the infection will be forced to die out. The key is to work together (worldwide) and focus on vaccination to drive down R0 and levels of virus circulation[4]. With less virus circulating, there is less opportunity for the virus to mutate into new variants.

RNA viruses, such as SARS-CoV-2, evolve slowly. Therefore, it is thought current vaccines should remain effective against COVID-19 for at least a year. Research scientists are working on vaccine tweaks to protect against new variants - a much quicker process than creating vaccines from scratch, as only minor changes to the existing vaccines are required[2, 4, 6]. Also, less volunteers are needed in these trials, further speeding up the process[4].

Image: memyselfaneye (Pixabay)

The Misinformation pandemic

· Public citizens/peers,

· Government,

· Scientists[6].

A common misconception by many people is that mRNA vaccines are “gene therapy” and not actually vaccines, because they think the injected mRNA alters human DNA. This does not happen - after the mRNA has passed on its message, it just breaks down and degrades in a harmless manner[6].

The future

Yearly vaccine boosters:

It is unlikely COVID-19 will completely disappear - instead, it is expected to become a background infection (endemic). We will probably need an annual booster for the immediate future, particularly to protect the vulnerable[4, 6].

Changed behaviour:

There is likely to be an improved attitude towards infection - changing behaviour to prevent infection risk - similar to attitude/behaviour changes towards accidents. Historically, accidents were a common cause of death, but this gradually changed over the years with improved preventative measures[6]. The public are now more aware about the importance of handwashing and ventilation, but other bad habits still need to be addressed, including the UK culture of going into work when unwell[6].

Targeted strategies: Identifying the spreaders:

It is unclear whether spreaders are adults returning home from work, and/or children returning from school. When this has been identified, better targeted health strategies can be introduced to protect the community[2]. Governments are expected to prepare improved response systems to mitigate pandemic spread of emerging future viruses[6].

Utilising technology:

The latest generation vaccines (mRNA and replication-incompetent vector) are as good as, if not better than traditional vaccines. There is very promising potential to use this technology to protect us against other prevalent diseases, including cancer[2].

Future research initiatives:

· Preventing long-haul COVID[6].

· Investigating the impact of the vaccines in long-haul COVID patients[6].

· Research into vaccinating children to protect the community[6].

Lessons learnt:

· The countries suffering least from this pandemic were those with a quick and decisive response: Taiwan learnt from the SARS epidemic in 2003 and reacted quickly. The UK (and other countries) need a quicker and more decisive response the next time an infectious disease emerges[2].

· This pandemic has highlighted some serious inequalities within society needing to be addressed[2].

· Global vaccination is needed to control this pandemic[2].

Image: Aksh Kinjawadekar (Pixabay)

Returning to ‘normal’


Image: Gerd Altmann (Pixabay)


2. Prof. Brian Cox, Prof. Melinda Mills, Prof. Charles Bangham and Dr Rino Rappuoli: The Royal Society, 2021. The Race for a Vaccine.

3. ZOE Symptom Study, 2021. ZOE Symptom Study.

4. Dr Anna Goodman and Prof. Tim Spector: ZOE Symptom Study, 2021. Covid-19 Vaccines: What we know so far.

5. University of Southampton, 2021.University of Southampton.

6. Prof. John Holloway, Prof. Rob Read, Prof. Saul Faust and Prof. Lucy Yardley OBE: University of Southampton, 2021. Beating COVID-19 - Vaccines, Trials and Prevention.

7. The Open University, 2014. SK320 Infectious Disease and Public Health: Block 1.

8. GOV.UK, 2021. Information for UK recipients on Pfizer/BioNTech COVID-19 vaccine.

9. GOV.UK, 2021. Regulatory approval of COVID-19 Vaccine AstraZeneca.

10. World Health Organization, 2021. COVID-19 Vaccines.

11. Amit, S., Regev-Yochay, G., Afek, A., Kreiss, Y. and Leshem, E.: The Lancet, 2021. Early rate reductions of SARS-CoV-2 infection and COVID-19 in BNT162b2 vaccine recipients.

12. World Health Organization, 2021. WHO lists two additional COVID-19 vaccines for emergency use and COVAX roll-out.

More from What’s on Watson’s Plate

· Guest Blog: Mythbusting the Coronavirus Vaccine

· Probably ‘That’ Coronavirus: My Symptoms

· Week 52 Health Diary: One Year Review: Let’s Start at the Very Beginning…

· Week 0 Health Diary: The Starting Point (I’ve got to do this!)

MSc Nutrition & Behaviour, BSc Health Sciences. Health Blogger:

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